I'm playing Pokemon HeartGold on my iPhone and I love it!
I installed Ignited via SideStore. No Jailbreaking necessary. Not computer tether. SideStore can renew the side loaded emulator every 7 days when on WiFi. The iPhone is perfect for DS emulation with a stylus.
(Ignited is a fork of Delta with more options, and SideStore is a fork of AltStore, with no computer tether needed)
I play Pokemon via PokeMMo and I urge you to check it out! It's available for desktop, mac, Android and iOS. You just need the roms of the games you want to play and then you create your character and choose your starting region.
Sure! It's an app/game you download which uses the Roms of the different games to enable you to play Pokemon online with other players, but you don't have to engage with them. You can also choose to just play each game as if you were offline and then transition into a new region after the top four, while having access to your pokemon from the old region. It's a lot of fun, but the devs rebalanced the games a bit, which makes it a bit harder, but still fair :)
Here's the link where you can find more information:
https://pokemmo.com/en/
Can also vouch for pokemmo, it's like Pokémon but better. Global trade market, large playerbase, slightly more difficult than traditional Pokémon games, travel between kanto, johto, hoenn and unova as the same character (fire red/leaf green, heartgold/soulsilver, emerald, black/white)
It truly is the Pokémon game Nintendo will never make and I'll never go back to playing the normal games, it's that good.